The present disclosure relates to an inkjet recording apparatus for recording by ejecting ink to a recording medium such as a paper sheet.
Recording apparatuses such as a facsimile, a copier, a printer, and the like are configured to record an image on a recording medium such as a paper sheet, an OHP sheet, or the like, and can be classified into an inkjet type, a wire dot type, a thermal type, and the like in accordance with methods of recording. In addition, inkjet recording methods can be classified into a serial type in which recording is performed by a recording head scanning the recording medium and a line head type in which recording is performed by a recording head fixed to the recording apparatus main body.
For instance, the line head type inkjet recording apparatus is equipped with a line head type inkjet head (recording head) for each color, in which ejection nozzles are aligned at a predetermined interval in the entire width of a printing area perpendicular to a transport direction of the recording medium. Further, ejection nozzles corresponding to printing positions eject ink in synchronization with transportation of the recording medium so as to print on the entire recording medium.
In this inkjet recording apparatus, the recording medium after printing by the recording head causes upward or downward warp as the ink is dried, and hence the transportation of the recording medium is apt to be unstable. In order to suppress the warp of the recording medium, it is preferred to decrease an interval between transport paths for the recording medium after printing as much as possible. On the other hand, when the interval between transport paths is decreased, there occurs a problem that wet ink adheres to a transport guide or that the adhered ink is retransferred to the recording medium so as to cause offset.
Therefore, there is known a recording apparatus in which a recording surface side of the transport path is opened from recording means to discharging means, and among discharge rollers and discharge spur rollers constituting the discharging means, an outer diameter of the discharge spur roller on the recording surface side is made larger than an outer diameter of the discharge roller on a back side.
In addition, there is known an inkjet recording apparatus in which a paper sheet pressing member opposed to the recording surface of the paper sheet is disposed, and the paper sheet pressing member presses width direction end portions of the paper sheet transported along a rib of a print receiving member so that warp of the paper sheet is suppressed. Further, there is known an inkjet printer equipped with a plurality of guiding curved members for guiding the recording medium after printing to a discharge tray in such a manner that positions of the width direction end portions of the recording medium are higher than a position of a width direction center portion.
However, in the method of setting the outer diameter of the discharge spur roller on the recording surface side to be larger than the outer diameter of the discharge roller on the back side, because the recording surface side of the transport path is opened, a leading end of the recording medium cannot enter a nip between the discharge roller and the discharge spur roller when a warp exceeding a supposed range occurs in the recording medium. As a result, there occurs a problem, such as a jam or skew of the recording medium, or a conspicuous image defect is generated.
In addition, in the method of suppressing warp of the paper sheet by pressing width direction end portions of the paper sheet transported along a rib of the print receiving member by the paper sheet pressing member, the paper sheet is transported in a state where the paper sheet is sandwiched between the paper sheet pressing member opposed to the recording surface of the paper sheet and the rib opposed to the surface opposite to the recording surface. Therefore, an image recorded on the recording surface of the paper sheet may be rubbed and damaged by the paper sheet pressing member.
In addition, in the method of using the plurality of guiding curved members for guiding the recording medium after printing to the discharge tray in such a manner that positions of the width direction end portions of the recording medium are higher than a position of the width direction center portion, the recording medium is transported in a state where the guiding curved members support the lower surface of the recording medium so that positions of the width direction end portions are higher than a position of the width direction center portion. Therefore, the recording medium can be stably supported when the width direction center of the recording medium warps downward, but the recording medium may not be stably supported when the width direction center of the recording medium warps upward. Further, in this structure, the recording medium is transported in a state where one width direction end of the recording medium contacts with a reference wall. Therefore, upward or downward warp of a small size recording medium cannot be suppressed symmetrically in the width direction.